Is this a good co2 setup feed back needed

My grow room is 702 cubic ft. I will be running a 20lb co2 tank(with a regulater set on a timerfor about 15 plants. My cycle will be 3hrs of co2 1hr of exhaust. so i will go through this cycle about 6 times per day. in each cycle it will take 2hrs to fill and during the last hr the tank will continue pumping co2 at the set limit of .42cfh My intake clears the room in 2 min. and i would need a refill once a month is there any adjustments I need to make to get better results. all feedback is appreciated

Thats over kill, why would you run for 3hrs?
Run for like 20min and leave the room sealed for
3hrs then vent.

yes dude, 3 hrs is was to long. you would go thru a tank in 2 weeks. I used that co2 calculator and it was way off. got a controller and it comes on for 1 min every 5 min. keeps it at 1500 ppm perfect. there are to many variables with using the calculater.

Your first co2 attempt huh lol your tank willl be empty in a day lol..I turn my tank on for roughly 3 minutes every hour for a 8x8 room. Then every 2 hours 10 minutes before a fill I have my fan set to come on for 8 minutes then it goes off and the damper closes.2 minutes later co2 refills the room. Do this only on lights on during flower. Never at dark times and not needed for veg.

Thanx alot I appreciate the correction and feed back!!!!